The Steamboating Forum

]Yesterday I was calculating how to install a pre-startup lubrication system on my 2 cylinder simple engine. Ironically, today I had a chance to go through the cast-off bits of an old fire engine & among some great valves there was a Swift pump oiler with a 3/8 npt outlet that was designed to do what I need exactly. A little cleaning & a new valve wheel & it will be serviceable.

My question now is the location of the oiler; I have an opening between the throttle & the split to the 2 cylinders or I have an opening at each of the fittings feeding directly to each steam chest. The steam chest feed would require a T in the feed line & I fear that one cylinder could get all of the oil & not be detectable. Advice would be very helpful, thank you.

Oddly enough, I just dealt with such a problem. On a telescope of all things.

On telescopes above a certain size, the moving part (most of it) is supported on oil lubricated plain bearings. It is important that none of the three or four bearings 'hog' the oil. The elegant and simple solution is to use a relatively generous bore pipe from the pump to the dividing manifold and then run very small bore pipes (called capillary tubes) from the manifold to each bearing.

In your case two things are on your side.

First, that you are oiling the engine when there is no pressure in any part of it. You did call it pre oiling.

Second, by running an ordinary copper tube (1/4"?) from the pump to the tee and then running teeny little tubes from there to the steam chests or cylinders you will get fairly decent balance even when lubricating under pressure.

Now as to where to get those small tubes, I call on the rest of the crew to chime in. I need to buy some small S.S. tubing for a tea cup heater so I'm all ears.

teeny tiny tubes are readily obtained from mcmaster of course...

stainless for really small, otherwise 1/8" brass & copper.

- Bart

The line to the junction isn't that important but the two lines after it need to be smaller than that. Like 1/16" bore or less perhaps. Shorter length calls for smaller bore.

The theory behind this is that the pressure drop across the small tubes needs to be fairly high. If it's working right, there will not be that much difference in the force needed to move your pump handle whether there is pressure in the engine or not. The pressure drop in the small bore tube dominates the equation, so to speak.

In fancy systems there is a separate pressure regulator in each feed line after the junction. The capillary tube solution works so well (and more simply) that even on rather large bearings it has become the design of choice.

The most recent telescope I have seen this on is in Hawaii on Mauna Kea at Keck one and two. The moving mass supported is four million kilograms (5000 tons!) and this is supported on four pads of about a foot by four feet. The static friction is zero and when the drive system is disengaged the telescope moves in the breeze. The oil film is a couple of thousandths thick and has a modulus about the same as steel. All highly non-intuitive for me. I was impressed.

That's about 4000 psi loading on those pads... at what pressure is the oil fed to the pads?

- Bart

Dunno but the pump is fairly far away to avoid any heat near the telescope. I could be off on the pad sizes. I looked at them from a distance. I am not among the anointed who get to clamber about.

The electric motor that moves the beast is way cool. It's made up of about a zillion permanent magnets mounted on a forty foot diameter ring on the base of the scope and another zillion electromagnets on a fixed ring about a millimeter away from the permanent magnets. Just a big permag motor that only turns one rev per day. No gears!

Getting way off of steam subjects here. Sorry.

While searching around surplus metal junkyards I found much surgical stainless steel tubing, I think it is used to make medical needles, I don't know. But since the price was $1.50 per pound (stainless scrap price at the time) I bought about a hundred 20 feet lengths of it. I think it is around 1mm outside diameter.

If anyone needs some I could cut some off and mail it. Lengths of 8 inches or so would fit into an envelope. Longer lengths can be coiled, but would need about 12 inch diameter coil size to avoid kinking.

I have made connections by silver soldering the 1mm tube into 1/4 inch diameter tubing, then use conventional fittings such as Swagelok. The tubing is cut with ordinary pliers, then the cut end (which has been crimped shut by the cut) needs to be ground with a fine Dremel wheel to open up the inside diameter. One must be careful to have the end of the tubing standing above the molten silver solder to avoid sealing the end of the tubing while soldering.